This invention relates to a heat treating furnace and to a method of effecting thermochemical processing of a metal work load within a heated furnace chamber in the presence of a gas. Typical examples of gas heat treating processes are carburizing, decarburizing, reduction and nitriding.
In one exemplary process, the furnace chamber is evacuated to a high order of vacuum and then is heated to raise the temperature of the work. Thereafter, an appropriate processing gas is admitted into the chamber and is circulated past the work while the chamber is maintained at a controlled and usually sub-atmospheric pressure and while heating of the work is continued. Upon contacting the hot metal surfaces of the work, the gas decomposes to produce the desired surface characteristics, the gas in the chamber ordinarily being continuously replenished so as to keep a supply of active gas in the chamber.